Linear Actuator and Method of Operation Thereof

ABSTRACT

A method of locking a linear output member in a retracted position within a linear actuator, where the linear output member is capable of axial motion within a housing of the linear actuator, includes rotating a generally tubular rotor disposed within a rotary lock assembly of the actuator to a first rotor position, and shifting a lock capable of radial displacement within the rotary lock assembly based on rotating the rotor to the first position. The lock engages a radial groove of the linear output member when the linear output member is in a retracted position. The rotary lock assembly is constrained from axial motion. The radial groove of the linear output member includes an axially angled, substantially planar surface. The lock is configured to include an axially angled surface shaped complimentary to the axially angled, substantially planar surface of the radial groove.

This application is a divisional of and claims the benefit of priorityto U.S. patent application Ser. No. 12/983,042, filed Dec. 31, 2010 andentitled “Linear Actuator and Method of Operation Thereof”, the contentsof which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates generally to linear actuators. Moreparticularly, aspects of the disclosed embodiments relate to linearactuators that can be locked in position.

2. Description of Related Art

Conventional linear actuators have output rams that may be driven from arotary source or with pneumatic or hydraulic pressure. The actuator mayhave a lock mechanism to retain the output in a fixed position. Knownlock mechanisms, such as taught by Tootle in U.S. Pat. No. 4,463,661,engage an actuator synchronization system, and therefore provide onlyindirect locking to the output ram. Direct locking mechanisms thatemploy a linear actuator have been developed and typically include amulti-piece housing with increased size and mass. Such actuators includetine locks, an example of which is disclosed by Carlin in U.S. Pat. No.5,267,760. While some tine lock arrangements may allow for asingle-piece housing actuator, they have the disadvantage of usingflexing lock element with consequential fatigue considerations. LockingActuators can be operated by a rotary source rather than hydraulicallyor pneumatically. Present rotary source operated actuators, such asdisclosed by Grimm in U.S. Pat. No. 4,603,594, have the disadvantage ofrequiring an electrically operated solenoid mechanism (or othermechanical input separate from the rotary source) to unlock the actuatorlock before motion of the ram can commence. Ball Lock mechanisms such astaught by Sue in U.S. Pat. Nos. 4,703,683, Deutch in U.S. Pat. No.4,240,332, and Della Rocca in U.S. Pat. No. 4,742,758 have thedisadvantage of a low external load carrying capability of the rambecause of the point contact stresses imposed on the lock balls. Linearmotion lock sleeve and key arrangements, such as disclosed by Kopecek(the inventor of the present disclosure) in UK patent GB2435877, includea rotary-to-linear motion conversion mechanism for the lock sleeve andcomplexity associated therewith. Accordingly, it would be desirable toprovide a linear actuator arrangement that overcomes at least some ofthe problems identified above.

BRIEF DESCRIPTION OF THE INVENTION

As described herein, the exemplary embodiments overcome one or more ofthe above or other disadvantages known in the art.

One aspect of the disclosed embodiments relates to a linear actuator.The linear actuator includes a housing, a linear output member, and arotary lock assembly. The linear output member includes a radial grooveand is axially movable from a retracted position within the housing. Therotary lock assembly is constrained from axial motion within the housingand includes a rotor and a lock. The rotor is capable of axial rotationfrom a first to a second position. When the linear output member is inthe retracted position, the rotor surrounds the radial groove. When therotor rotates to the first position, the lock engages the radial groovewith radially moving lock keys and prevents axial motion of the outputmember from the retracted position.

Another aspect of the disclosed embodiments relates to a method oflocking a linear output member capable of axial motion in a retractedposition within a housing of a linear actuator. The method includesrotating a rotor disposed within a rotary lock assembly constrained fromaxial motion to a first rotor position. The method further includesshifting a lock key within the rotary lock assembly as the rotor rotatesto the first rotor position.

A further aspect of the disclosed embodiments relates to a linearactuator including a housing, a linear output member, a rotor, and alock. The linear output member includes a radial groove and is axiallymovable from a retracted position within the housing. The rotor isdisposed within the housing surrounding and coaxial with the linearoutput member. The lock is disposed within a bore of the rotor, and isresponsive to rotation of the rotor to a first rotor position to engageand be restrained within the radial groove of the linear output member.

These and other aspects and advantages of the exemplary embodiments willbecome apparent from the following detailed description considered inconjunction with the accompanying drawings. It is to be understood,however, that the drawings are designed solely for purposes ofillustration and not as a definition of the limits of the invention, forwhich reference should be made to the appended claims. Moreover, thedrawings are not necessarily drawn to scale and unless otherwiseindicated, they are merely intended to conceptually illustrate thestructures and procedures described herein. In addition, any suitablesize, shape or type of elements or materials could be used.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 depicts a front perspective view of a linear actuator inaccordance with an embodiment of the present disclosure;

FIG. 2 depicts a front perspective cross section view of a linearactuator in a locked position;

FIG. 3 depicts a cross section view of the linear actuator in FIG. 2 inaccordance with an embodiment of the present disclosure;

FIG. 4 depicts a front perspective cross section view of a linearactuator in an unlocked position;

FIG. 5 depicts a cross section view of the linear actuator in FIG. 4 inaccordance with an embodiment of the present disclosure;

FIG. 6 depicts a cross section view of a linear actuator in a lockedposition in accordance with an embodiment of the present disclosure;

FIG. 7 depicts a cross section view of a linear actuator in an unlockedposition in accordance with an embodiment of the present disclosure;

FIG. 8 depicts a cross section view of a linear actuator in accordancewith an embodiment of the present disclosure;

FIG. 9 depicts a cross section view of the linear actuator in FIG. 8 inaccordance with an embodiment of the present disclosure;

FIG. 10 depicts a cross section view of the linear actuator in FIG. 8 inaccordance with an embodiment of the present disclosure;

FIG. 11 depicts a cross section view of the linear actuator in FIG. 8 inaccordance with an embodiment of the present disclosure;

FIG. 12 depicts a cross section view of the linear actuator in FIG. 8 inaccordance with an embodiment of the present disclosure; and

FIG. 13 depicts a flowchart of process steps for locking a ram of alinear actuator in accordance with an embodiment of the presentdisclosure.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS OF THE DISCLOSURE

FIG. 1 illustrates a front perspective view of a linear actuator 100incorporating aspects of the disclosed embodiments. The actuator 100 hasan outer housing 104 and an output ram 108 (also herein referred to as a“linear output member”). FIG. 2 illustrates the output ram 108, which iscapable of axial motion (depicted by direction arrow X) into and out ofthe housing 104, such as from a retracted position as shown in FIG. 1.As a non-limiting example, the ram 108 may be attached to a door, panel,or engine thrust reverser, while the housing 104 is attached to a frameof a larger object, such as, but not limited to, an airplane. Movementof the ram 108 thereby determines position of the door, panel, or thrustreverser or other attaching surface. When the ram 108 is retracted intothe housing 104, it may be locked to prevent inadvertent or unintendedextension of the ram 108 from the housing 104. The aspects of thedisclosed embodiments provide a rotary lock mechanism for the linearactuator 100. FIG. 2 illustrates a rotary lock mechanism 112 includesaxially fixed lock keys that are displaced radially by grooves in thelock rotor 116 to engage a radial groove in the output ram 108, therebylocking and preventing axial motion of the ram 108 from its retractedposition. A Lock Ring 136 with internal grooves provides radial guidancefor the lock keys. An unlocked position of the rotor allows the keys todisengage from the radial groove, while a locked position of the rotorengages and restrains the keys within the groove.

FIGS. 2 and 3 depict cross section views of the actuator 100 with theram 108 retained within the housing 104 in a locked position via arotary lock assembly 112. In one embodiment, the rotary lock assembly112 includes a rotor 116 and a lock key 120 (also herein referred to asa “lock”). The ram 108 includes a radial groove 124, into which lock key120 may be disposed. Stated alternatively, while in the locked position,the lock key 120 engages the radial groove 124 of the ram 108 andprevents axial motion of the ram 108.

As shown in FIGS. 2 and 3, the rotor 116 is disposed coaxially with theram 108, and includes a bore 128 having an inner radius that interfaceswith a crown 132 of the lock key 120. A lock ring 136 is fixed to thehousing 104 and includes grooves 138 that guide the lock keys 120 andrestrict their displacement to radial motion, as will be described infurther detail below. In an exemplary embodiment, an inside radius ofthe bore 128 will be approximately equal to an outside radius of thecrown 132 when the lock key 120 is engaged with the radial groove 124.It will be appreciated that in response to the rotor 116 being disposedin the locked position of FIGS. 2 and 3, the bore 128 interfaces withthe crown 132 of the lock key 120 and the lock key 120 is restrainedfrom any outward radial motion (such as in direction Y in FIG. 2, forexample). Therefore, the lock key 120 engages and is retained or heldwithin, the groove 124 of the ram 108 by the rotor 116.

With reference to FIG. 2, in response to the engagement and retention ofthe lock key 120 within the groove 124, the ram 108 is axially locked.That is, motion of the ram 108, in response to any externally appliedtension in the X (axial) direction to the right of FIG. 2, is prevented.In response to an external tension load applied to the ram 108(attempting to pull thereupon without unlocking it first), the appliedload is reacted through the ram 108, and is transferred to the lock keys120 via groove 124. The lock keys 120 then react the applied tensionload into the lock ring 136, which is a fixed element, and which, inturn, reacts the load into the housing 104. Therefore, the ram 108remains securely locked within the housing 104 in response toapplication of external loading to the ram 108.

FIGS. 4 and 5 depict cross section views of the actuator 100 with therotor 116 in the unlocked position. Referring to FIGS. 3, 4, and 5, anexample rotor 116 includes three axial grooves 140, or recesses intowhich the crown 132 of each lock key 120 may be disposed, as illustratedin FIGS. 4 and 5. Disposal of the rotor 116 in the unlocked positionrenders it capable of receiving the lock keys 120 within the grooves 140and thereby defines an unlocked state. In the unlocked state, the ram108 is capable of axial extension from the retracted position, out ofthe housing 104, such as to the right of FIG. 4, for example.

In an embodiment, an aft edge (toward the left of FIG. 4) of the radialgroove 124 includes an axially angled surface 144 and an aft edge of thelock key 120 includes a corresponding axially angled surface 148 that iscomplementary to the surface 144 of the radial groove 124. Thestationary lock ring 136 includes an opening 152 having two guidancesurfaces 156 that engage with two surfaces 160 of the lock key 120. Theguidance surfaces 156 (FIG. 5) of the lock ring 136 are designed withappropriate clearances between the surfaces 156, 160 such that motion ofthe lock key 120 is constrained to the radial direction. In response tothe rotor 116 being in the unlocked position, the lock keys 120 are freeto disengage from the groove 124. Motion of ram 108 in the axialdirection, extending outward from the retracted position results inengagement of the angled surface 144 of the ram 108 with the angledsurface 148 of the lock key. Because of the geometry of the angledsurfaces 144, 148, a portion of the axial force accompanying motion ofthe ram 108 is resolved to a component that is directed radially outwardupon the lock keys 120. In response to the radially outward directedforce, and the constraint of the guidance surfaces 156, the lock keys120 withdraw, or move radially outwards, to the unlocked position, intothe grooves 140 of the rotor 116, as may best be seen in FIG. 5.

An embodiment of the disclosure may include a lock follower 162 that isof the same diameter of the ram 108 and is biased toward the directionof ram 108 extension by a spring 164. The lock follower 162 follows theram 108 as it initially extends and radially retains the lock keys 120in the withdrawn position as shown. This prevents the lock keys 120 fromfalling radially inward during or after extension of the ram 108, suchas may otherwise occur in response to ambient vibration, for example.

In one embodiment, the rotor 116 may be controlled and activated via alinear piston, such as a hydraulic or pneumatic piston, for example.FIGS. 6 and 7 depict cross section views of an actuator 100 having apiston and corresponding to the rotor 116 being in a locked and unlockedstate, respectively.

Referring to FIG. 6, a locking piston 168 is coupled to the rotor 116via a pin 170. In one embodiment, a nested spring arrangement 172 biasesthe locking piston 168 towards the right of FIG. 6, which corresponds tothe locked position of the rotor 116. This spring force bias assuresthat the lock rotor 116 remains in the locked position in the absence ofany external force, such as hydraulic or pneumatic pressure, as will bedescribed in further detail below.

An embodiment may also include a status indicator 176 to provide remoteindication whether the rotor 116 is in the locked or unlocked position.The status indicator includes a switch 180, a target 184, and a lock arm188. The lock arm 188 is coupled to the piston 168 and is responsive topiston 168 motion about pivot 192. As depicted in FIG. 6, in response tothe rotor 116 being in the locked position, the lock arm 188 ispositioned such that target 184 contacts switch 180, thus indicatingthat the rotor 116 is in the locked position.

An embodiment may include an additional interface, also known as a“catch” between the rotor 116 and the piston 168. An example of thecatch may include a shoulder 193 on the piston 168 designed to interfacewith a groove 195 of the rotor 116. The catch is designed such thatshould the pin 170 break, the rotor 116 cannot independently rotate or“walk away”, from the locked position to the unlocked position due tovibration. In the absence of such a catch, a failure of the pin 170(such as a broken pin, for example) could allow the switch 180 toindicate that the rotor 116 is in a locked position although it isactually in the unlocked position.

FIG. 7 depicts the piston 168, and thus the rotor 116, in the unlockedposition. With reference back to FIG. 6, it will be appreciated that thepiston 168 has shifted to the left, therefore causing the rotor 116, viapin 170, to rotate clockwise to the unlocked position. Motion of thepiston 168 from the locked position to the unlocked position causes thelock arm 188 to rotate counterclockwise about pivot 192 and thereforedisengage the target 184 from the switch 180. The switch 180 therebyindicates that the rotor 116 is in the unlocked position.

In an embodiment, the piston 168 may include two dynamic seals 196, 200(FIG. 7). Displacement from the locked position to the unlocked positionmay be accomplished via application of hydraulic or pneumatic pressurebetween the two dynamic seals 196, 200. If dynamic seal 196 is designedlarger than dynamic seal 200, as depicted, the differential area betweenthe seals 196, 200 creates a force that causes the piston to move to theleft. This movement of the piston 168 compresses the spring arrangement172 (FIG. 6), and the pin 170 that engages the rotor 116 moves to theleft, thus turning the rotor 116 clockwise to the unlocked position.

In an embodiment, the ram 108 may be actuated via pressure, such ashydraulic or pneumatic pressure, for example. With reference back toFIGS. 2 and 4, the ram 108 may include a dynamic seal 204, and theactuator 100 may include appropriate controls to apply pressure toeither an extend side 208 or a retract side 212 (shown to the left andright, respectively, of FIGS. 2 and 4) of the dynamic seal 204. Theextend side 208 of the ram 108 dynamic seal 204 may share porting withthe lock piston 168, such that application of pressure to the extendside 208 simultaneously applies pressure between the dynamic seals 196,200 of the lock piston 168. In this manner, unlocking and extension ofthe ram 108 may be accomplished via a single application of pressure.For example, in response to application of pressure to the extend side208 of the ram 108 dynamic seal 204, the lock piston 168 will bedisplaced from the locked position (to which it is biased by springarrangement 172) to the unlocked position, thereby rotating the rotor116 to the unlocked position. A portion of the axial force upon the ram108, exerted by application of pressure to the extend side 208 of theram 108, will be resolved by the angled surfaces 144, 148 to exert anoutward radial force upon the lock keys 120, which will be displacedinto the axial grooves 140 of the rotor bore 128, thereby allowingdisplacement of the ram 108 from the retracted position within housing104. The lock follower 162 follows the ram 108, and thereby holds thelock keys 120 in their withdrawn position within the grooves 140.

Following completion of the extension cycle, to retract the ram 108 andre-lock rotor 116, the extend side 208 of the dynamic seal 204 isdepressurized, and pressure is applied to the retract side 212 of thedynamic seal 204. Therefore, pressure is present on the right side ofthe dynamic seal 204. The ram 108 then retracts and pushes the lockfollower 162 out of the way (to the left of FIGS. 2 and 4). With thelock follower out of the way and the ram 108 in the retracted position,the lock keys 120 are aligned with the radial groove 124 in the ram 108.The spring arrangement 172 acts to push the lock piston 168 to the right(see FIGS. 6 and 7), causing the rotor 116 to rotate counterclockwise.Radially angled surfaces 213 of the groove 140 interface with theradially angled surfaces 215 (see FIG. 3) of the lock keys 120 proximatethe crown 132 of the lock keys 120 to resolve a portion of the rotaryforce into inwardly directed radial force and shift, or displace thelock keys 120 into the radial groove 124 of the ram 108. As shown inFIG. 3, radially angled surfaces 213 of the grooves 140 and radiallyangled surfaces 215 of the lock keys 120 may be substantially planar andhave angles complementary to one another. The rotor 116 continuesrotating counterclockwise until the inner radius of rotor bore 128rotates over the crown 132 of the lock keys, thus causing the ram 108 tobe securely retained in the locked position. As shown in FIG. 5, thecrowns 132 of the lock keys 120 may have a rounded outer surface with aradius of curvature substantially the same as a radius of curvature ofan inner surface of the rotor 116.

In an embodiment, it may be desirable to synchronize the motion ofmultiple actuators 100. With reference to FIG. 2, the actuator 100 mayinclude a synchronization arrangement such as a ball nut 216, a ballscrew 220, a worm gear 224, and a worm 228 having a coupling 232, forexample. The ball nut 216 is coupled to, or fixed within the ram 108,such that it travels axially with the ram 108 as it either extends orretracts. The ball nut 216 is also engaged with the ball screw 220 in afashion that would readily be appreciated by one of skill in the art,such the ball screw 220 is responsive to axial motion of the ball nut216 to rotate abut the center axis X. The worm gear 224 is fixed to theball screw 220 and therefore rotates as the ball screw 220 rotates (anarrangement known in the art as a “back-driving worm gear”). The wormgear 224 engages a worm 228 in a fashion that would readily beappreciated by one of skill in the art and is responsive to rotation ofthe worm gear 224 to rotate about the center of the worm 228. Thecoupling 232 (depicted in FIG. 2 as a star configuration) provides anexternal link of the depicted actuator 100 to similar couplings of otheractuators, thereby providing a mechanical, synchronizing linktherebetween.

While embodiments of the disclosure have been depicted and describedhaving pneumatic or hydraulic activation of the ram 108 and the rotor116, it will be appreciated that the scope of the disclosure is not solimited, and may include other means of ram 108 and rotor 116activation. For example, the pressurized system used to drive the ram108 and the locking piston 168 may be replaced with a planetary(epicyclic) gear arrangement coupled to the ball screw 220 to drive theram 108, as will be appreciated by one of skill in the art.

FIG. 8 depicts an exemplary embodiment of a mechanical driven actuator101. The mechanical actuator 101 includes an epicyclic gear arrangement236 having a sun gear 240, planet gear 244, ring gear 248, and a planetcarrier 252. The planet gear 244 is engaged with both the sun gear 240and the ring gear 248. Because general operation of an epicyclic geararrangement is understood within the art, a full description is notnecessary here.

The sun gear 240 of the planetary gear arrangement 236 may provide themechanical drive input to the gear arrangement 236 and the planetcarrier 252 couples the ball screw 220 to the planet gear 244 to providethe energy to extend and retract the ram 108. An outer diameter of thering gear 248 (annulus) of the planetary gear arrangement 236 may benested in a bearing race and directly attached to the rotor 116 via arotor extension 256. Therefore, it will be appreciated that in thisembodiment, the ball screw 220 serves as the driver, and the ram 108 isresponsive to the rotation of the ball screw 220 to move axially.

In an exemplary embodiment, rotation of the rotor 116 to move to theunlocked position, may be provided by the planetary gear assembly 236initially operating in what is known as a “Star” mode, during a lostmotion stroke. With reference to FIG. 10, the rotor extension 256 (whichis coupled to ring gear 248) acts as a key that engages a radial slot260 that is equivalent to (and thereby defines) the rotation of therotor 116 from the locked to unlocked position. In an embodiment, atorsion spring (analogous to spring assembly 172) may be included thatdirectly biases the rotor 116 to the locked position.

Referring to FIGS. 8 and 9 together, to extend the ram 108, energy isinput (such as via a motor, for example) to the sun gear 240. Becausethe ram 108 is constrained from any axial motion by the lock keys 120,the ball screw 220 cannot turn and advance the ram 108. Therefore, thecarrier 252 is locked until the lost motion unlocks the lock keys 120.Therefore, the only response to the rotation input by the sun gear 240is to rotate the ring gear 248, which is coupled to the rotor 116. Theunlocking of the lock keys 120 in response to rotor 116 rotationmechanically coincides with the rotor extension 256 bottoming out in theslot 260 of the housing 104. Bottoming out of the extension 256 in theslot 260, and unlocking the lock keys 120, thereby results in lockingthe ring gear 248 and freeing the planet carrier 252 to allow the planetgear 244 to revolve around the sun gear 240. Thus, the planetary geararrangement 236 changes from star mode (fixed planet carrier 252, freesun 240 and free annulus 248) to planetary mode (fixed annulus 248, freesun 240 and free planet carrier 252). In the planetary mode, the energyinput to the sun gear 240 is used to cause the planet gear 244 torevolve around the sun gear 240, and drive the planet carrier 252,which, in turn drives the ball screw 220 and thereby, via ball nut 216,causes the ram 108 to move axially.

To retract the ram 108 and rotate the rotor 116 to the locked position,this process is reversed. The motor driving the sun gear 240 reversesdirection. The ring gear 248 reverses the load direction and attempts torotate the rotor 116 from the unlocked position to the locked position.However, the lock keys 120 are constrained in the withdrawn positionwithin the grooves 140 of the rotor 116 by the lock follower 162, andthereby prevent any rotation of the rotor 116. This effectively locksthe ring gear 248 (via rotor extensions 256), and defines the planetarymode. Therefore, the input rotation of the sun gear 240 is transferredto the carrier 252, which causes the ball screw 220 to rotate, andretract the ram 108.

In response to the ram 108 coming to the fully refracted position, thelock follower 162 is pushed out of the way (axially) by the ram 108 andthe lock keys 120 are aligned with the radial groove 124 in the ram 108.In response to the ram 108 being fully retracted, and thus no longercapable of any further axial motion, the ball screw 220 (and thus planetcarrier 252) is locked, and the planetary gear arrangement 236transitions from planetary mode to star mode. This now allows the rotor116 to rotate from the unlocked to the locked position, pushing the lockkeys 120 radially inward into the groove 124 via the interfacingsurfaces 213, 215 of the rotor 216 groove and lock crowns 132,respectively, thus re-locking the ram 108 as described herein.

It will be appreciated that the output rotation direction of the ringgear 248 and rotor 116 during the lost motion stroke (star mode) isopposite of that of the planet carrier 252 and ball screw 220 duringextension of the ram 108 (planetary mode). This is a fundamentalcharacteristic of epicyclic gears operated in both Star and Planetarymodes. This lost motion feature results in a design that is self-lockingand self-unlocking without any additional commands or signals requiredin addition to the drive torque.

To increase clarity, additional cross sectional figures of the actuator101 as described herein and shown in FIG. 8 are provided. FIG. 10depicts a cross section view of the planetary arrangement 236 shown inFIG. 8 including the sun gear 240, planet gear 244, ring gear 248, andplanet carrier 252. FIG. 11 depicts a cross section view of theplanetary arrangement 236 shown in FIG. 8 including the ring gear 248,planet carrier 252, and rotor extension 256. FIG. 12 depicts a crosssection view of the rotor 116 with lock keys 120 in the locked position.

In view of the foregoing, FIG. 13 depicts a flowchart of exemplaryprocess steps of a method for locking a linear output member of a linearactuator, such as locking the ram 108 in a retracted position within theactuator 100, for example. Process step 300 includes rotating the rotor116, disposed within the rotary lock assembly 112 of the actuator 100 toa first, locked rotor position, the rotary lock assembly 112 beingconstrained from axial motion within the housing 104 of the actuator100.

In response to rotating the rotor 116 to the first, locked position,process step 310 includes shifting the lock key 120 within the rotarylock assembly 112 to engage the radial groove 124 of the ram 108. Itwill be further appreciated that in response to rotating the rotor 116to the first, locked rotor position, the lock key 120 is restrainedwithin the radial groove 124 of the ram 108 by the inner radius of therotor bore 128. The process may further include rotating the rotor 116to the second, unlocked rotor position, and thereby providing theclearance and degree of freedom for the lock keys 120 to shift radiallyoutward into the axial groove 140, allowing the lock keys to disengagefrom the radial groove 124. Because of the interfacing surfaces 144,148, axial motion of the ram 108 from the retracted position results inresolving some axial force into a radial force component to disengagethe lock keys 120 from the radial groove of the ram 108.

As disclosed, some embodiments of the present disclosure may includeadvantages such as: an ability to provide robust, direct locking of theram using a single piece housing having reduced overall size in at leastone of length and diameter as well as mass; an ability to initiatelocking and release of a linear ram without a separateelectrical/hydraulic/pneumatic and/or mechanical locking or unlockingcommand or signal; and, a simple locked load path to provide enhancedreliability.

While embodiments of the disclosure have been described having a rotorwith three axial grooves, it will be appreciated that the scope of thedisclosure is not so limited, and is contemplated to include rotorshaving other numbers of grooves that may include helical grooves, suchas one, two, four, or more grooves, for example. Further, whileembodiments of the disclosure have been described controlling the rotorvia a linear piston, it will be appreciated that the scope of thedisclosure is not so limited, and is contemplated to include pistonsthat may be controlled via alternate means, such as linear motors orsolenoids, for example. Additionally, while embodiments of thedisclosure have been described with a coupling having a starconfiguration, The coupling 232 (depicted in FIG. 2 as a starconfiguration) it will be appreciated that the scope of the disclosureis not so limited, and is contemplated to include other means of torquetransmission geometry, such as square, hexagonal, octagonal, TORX, etc,for example.

Thus, while there have been shown, described and pointed out,fundamental novel features of the invention as applied to the exemplaryembodiments thereof, it will be understood that various omissions andsubstitutions and changes in the form and details of devicesillustrated, and in their operation, may be made by those skilled in theart without departing from the spirit of the invention. Moreover, it isexpressly intended that all combinations of those elements and/or methodsteps, which perform substantially the same function in substantiallythe same way to achieve the same results, are within the scope of theinvention. Moreover, it should be recognized that structures and/orelements and/or method steps shown and/or described in connection withany disclosed form or embodiment of the invention may be incorporated inany other disclosed or described or suggested form or embodiment as ageneral matter of design choice. It is the intention, therefore, to belimited only as indicated by the scope of the claims appended hereto.

1-14. (canceled)
 15. A method of locking a linear output member in aretracted position within a linear actuator, the linear output membercapable of axial motion within a housing of the linear actuator, themethod comprising: rotating a generally tubular rotor disposed within arotary lock assembly of the actuator to a first rotor position, therotary lock assembly being constrained from axial motion; and shifting alock capable of radial displacement within the rotary lock assemblybased on rotating the rotor to the first position such that the lockengages a radial groove of the linear output member when the linearoutput member is in a retracted position; wherein the radial groove ofthe linear output member includes an axially angled, substantiallyplanar surface; and wherein the lock is configured to include an axiallyangled surface shaped complimentary to the axially angled, substantiallyplanar surface of the radial groove.
 16. The method of claim 15, furthercomprising: restraining the lock within the radial groove of the linearoutput member based on a substantial portion of the axially angledsurface of the lock being in contact with a substantial portion of theaxially aligned, substantially planar surface of the radial groove. 17.The method of claim 16, further comprising: rotating the rotor to asecond rotor position; and allowing the lock to disengage the radialgroove of the linear output member.
 18. The method of claim 17, furthercomprising: moving the linear output member from the retracted position;and disengaging the lock from the radial groove of the linear outputmember. 19-20. (canceled)
 21. The method of claim 16, wherein the stepof rotating a generally tubular rotor disposed within a rotary lockassembly of the actuator to a first rotor position further comprisesrotating a generally tubular rotor having an inner surface having aradius of curvature; and wherein the step of restraining the lock withinthe radial groove of the linear output member further comprisesrestraining the lock configured with a crown extending radially outward,the crown having a rounded outer surface with a radius of curvaturesubstantially the same as a radius of curvature of the inner surface ofthe rotor, wherein a substantial portion of the rounded outer surface ofthe crown corresponds to and contacts the inner surface of the rotor.22. The method of claim 18, wherein the step of disengaging the lockfrom the radial groove of the linear output member further comprisesresolving an axial force, accompanying moving the linear output memberfrom the retracted position, to a component directed radially outwardlyupon the lock such that the lock is thereby moveable radially outwardlyfrom the radial groove.
 23. The method of claim 18, wherein the step ofrotating the rotor to a second rotor position further comprises rotatingthe rotor having an inner surface and an outer surface, the innersurface of the rotor including a plurality of axial rotor grooves, eachaxial rotor groove having a rounded surface with a radius of curvaturedefining an outer radius of the axial rotor groove and radially angledsurfaces between the outer radius of the axial rotor groove and aninnermost radius of the rotor; and wherein the step of disengaging thelock from the radial groove of the linear output member comprisesdisengaging the lock configured with a crown having a first portion anda second portion, the second portion extending radially outward from thefirst portion, the crown further configured with a radially angledsurface between the first portion and the second portion, the radiallyangled surface having an angle complementary to an angle of one of theradially angled surfaces between the outer radius of the axial rotorgroove and the innermost radius of the rotor; wherein the one of theradially angled surfaces between the outer radius of the axial rotorgroove and the innermost radius of the rotor is corresponding to and insubstantial contact with the radially angled surface between the firstportion and the second portion of the crown.
 24. The method of claim 15,wherein the step of rotating the rotor further comprises translating apiston capable of linear motion to a first piston position correspondingto the first rotor position, the piston being operatively connected tothe rotor.
 25. The method of claim 18, further comprising: returning thelinear output member to the retracted position; returning the rotor tothe first rotor position; and engaging the lock with the radial grooveof the linear output member.